Planar waveguides in glass have been of interest for some time for making low-cost,high-performance passive optical components such as ring resonators, couplers, splitters and wavelength division multiplexers. Currently, two processes are widely used for making planar waveguides in glass. The first method is ion exchange that uses a glass substrate containing mobile ions which can be locally exchanged for another ion which will increase the refractive index. For example, a glass containing sodium ions could be masked to define a waveguide path, then immersed in a molten potassium salt bath where the sodium would be exchanged for the potassium, which would result in a higher index of refraction in the path and create a waveguide. This ion exchange technique has certain shortcomings. The waveguide is formed on the surface of the glass and losses are associated with the top surface roughness and with ionic defects occurring during the exchange. Recent advances in this technology have led to propagation losses of 0.01 dB/cm, but this requires careful fabrication techniques including judicious choice of materials and glass substrate composition and precise process control. Another technique is to grow glass on a silicon substrate by flame hydrolysis deposition (FHD) and form waveguides by reactive ion etching. Losses of 0.01 dB/cm have been achieved. This process is the same as that which is used to make fiber optic preforms from which telecommunications grade fiber can be drawn. The fiber has a loss of 1 dB/Km or 10.sup.-5 dB/cm, three orders of magnitude lower than losses achieved in planar form. The material, therefore, cannot be the cause of the losses in planar form. Waveguides formed by this process employ masking and subsequent etching to remove portions of the substrate and leave the raised, ribbed waveguide. A number of different etching techniques can be used. Etching techniques, however, leave the ribbed waveguide with rough edges that contribute to higher losses. Further processing is required to attempt to reduce the roughness and produce smoother boundaries.